Polyvinyl chloride (PVC) based films and film based assemblies are used in numerous medical products. However, PVC is viewed as hazardous to both the environment and to personal health. Incineration of PVC results in the release of hydrochloric acid (HCl), and PVC is viewed as a major contributor to HCl in incinerator flue gases. Also, PVC is suspected of contributing to polychlorinated dibenzodioxin and furan toxins formed during incineration. Levels of these toxins are up to three times greater in medical infectious waste as compared to municipal waste streams. In addition to incineration concerns, exposure to di-2-ethylhexyl phthalate (DEHP), a common plasticizer used with PVC, may present a number of health related concerns, including reduced blood platelet efficacy and potential links to liver cancer.
Despite these concerns, PVC-based films and film based assemblies, continue to be the material of choice in scientific and medical applications. See, e.g., Encyclopedia of Polymer-Science and Technology, Vol. 17, pg. 50 (1989). The continued use of PVC materials is due, at least in part, to PVC's attractive qualities, including flexibility; toughness; resistance to UV light, solvents, cuts, scratches, and acids; clarity or opaqueness as required; and low cost. In addition, PVC's characteristics can be modified through the addition of various additives, such as plasticizers, colorants, and the like. For example, U.S. Pat. No. 4,298,714 discloses a modified PVC material with reduced hydrophilicity due to the addition of various thiol-group compounds to the PVC backbone.
Other thermoplastic polymers have been used to form single-layer films and film based assemblies, For example, low-density polyethylene, high density polyethylene, polypropylene, ethylene vinyl acetate, and polybutylene have all been used to form single-layer films and film based assemblies. Encyclopedia of Polymer Science and Technology, ibid., pp. 50-51. Further, films developed for replacement of PVC are often made of polyolefins. Polyolefins have low surface energies and are often difficult to bond with conventional adhesives or solvents. Consequently, none of these polymer materials has been successfully used to provide films and film based assemblies with the advantageous characteristics needed to serve as environmentally compatible replacements for PVC-based materials.
The problem is particularly acute with respect to tubing assemblies with cassettes used in connection with infusion pumps for metering IV fluids to a living patient. Cassettes, for example as taught in U.S. Pat. 4,236,880 to Archibald, must be highly flexible so as to deform in the manner of a rolling diaphragm when pressed by a pumping piston. They must additionally be tough enough to withstand repeated deformation for extended periods of time: 72 continuous hours is a typical institutional requirement among U.S. hospitals. Such cassettes are prepared by compression blow molding such that the material must be able to form a secure heat bond during the fabrication.
In addition to continued environmental incompatibility, these films and film based assemblies tend to delaminate during continuous usage. To avoid delamination problems, U.S. Pat. No. 3,561,493 provides a multilayered film in which the inside and outside layers are welded together by a precompounded layer of the two different polymers. However, chlorine-containing polymers, such as PVC, are still considered best for use in such films and film based assemblies.
To date, no films and film based assemblies exist which provide the advantageous characteristics of PVC materials, and yet are environmentally compatible upon disposal.
Therefore, there is a need for films and film based assemblies that can be utilized in a wide range of both medical and nonmedical products, and that can serve as replacements for PVC-based materials. There is a need for elements of medical devices such as IV infusion therapy sets which are environmentally compatible, and yet capable of satisfying the challenging requirements. Specifically, there is a need for PVC replacement cassettes, IV sets and medical films which are extremely flexible, yet tough enough to endure their intended use. They must be capable of being heat bonded, must be visually transparent, as well as solvent and UV light resistant, and capable of being made for a relatively low cost.